Self-bondable printing paper

ABSTRACT

The invention is directed to coated papers, which has been coated with a new and improved coating composition for imparting thereto (1) the printing properties of typical clay-coated printing papers and (2) heat sealing properties found in plastic films and plastic film-laminated papers. This paper comprises a white opaque paper substrate and an applied white opaque coating composition comprising an aqueous dispersion of 5-20 percent resinous binder, 15-75 percent opaque pigment such as inorganic pigment, and 20-65 percent discrete thermoplastic resin particles with a coalescing range of at least 140* F., and preferably 140*400* F., in which the above-listed percentages of components are based on the dry weight of the total dry solids content of the coating composition.

United States Patent Olson [45] May 23, 1972 [54] SELF-BONDABLE PRINTINGPAPER 211 App]. No.2 828,974

[52] U.S.Cl ..161/161, 117/14, 117/155, 117/161 UZ, 156/308, 161/162,161/165, 161/181, 161/251,161/253,161/254,161/255,161/256,

[51] Int. Cl. ..B32b 3/26, B32b 27/08, B32b 27/30 [58] Field of Search156/308; 161/247, 250, 251, 161/252, 254, 268, 270, 87, 238, 238, 265,266, 162,165,181, 255, DIG. 2; 162/124, 168; 281/21,

15; 117/15 T, 14, 161 UP; 260/233,3

[56] References Cited UNITED STATES PATENTS 2,306,400 12/1942 Menzel..161/DIG. 2 2,759,847 8/1956 Frost et a1.. 117/156 X 2,923,707 2/1960Wolff ..260/233 3 2,992,149 7/1961 Drelich 117/161 Ul-ll-l 3,028,2584/1962 Rice ..117/156 X 3,047,427 7/1962 Dratz 1 17/156 X 3,256,1386/1966 Welch et al.... ...162/124 3,313,803 4/1967 Roberts 260/233 33,351,479 11/1967 Fairchild ..117/156 X SHEETS AFTER APPLICATION OFPRESSUFE AND ENERGY THERMOPLASTIC RESIN IN COALESCE D FORM FOREIGNPATENTS OR APPLICATIONS 116,167 8/1940 Australia ..281/21 OTHERPUBLICATIONS Ellis, Carleton, The Chemistry of Synthetic Resins, Volume1, 1935, Reinhold Publishing Corp. New York NY. pages 792 and 828.

Lohnaset al ..117/156X vanWestrenen ..1 17/156 X Primary Examiner--.IohnT. Goolkasian Assistant Examiner-C. B. Cosby AttorneyChristen & Sabol[57] ABSTRACT The invention is directed to coated papers, which has beencoated with a new and improved coating composition for imparting thereto(1) the printing properties of typical claycoated printing papers and(2) heat sealing properties found in plastic films and plasticfilm-laminated papers. This paper comprises a white opaque papersubstrate and an applied white opaque coating composition comprising anaqueous dispersion of 5-20 percent resinous binder, 15-75 percent opaquepigment such as inorganic pigment, and 20-65 percent discretethermoplastic resin particles with a coalescing range of at least 140 Fand preferably 140400 F., in which the above-listed percentages ofcomponents are based on the dry weight of the total dry solids contentof the coating composition.

20 Claims, 2 Drawing Figures REGION OF SEA L REG ION OF SEA L PatentedMay 23, 197.2

INVENTOR ROBERT A. OLSON SELF-BONDABLE PRINTING PAPER BACKGROUND OF THEINVENTION 1. Field of Invention This invention relates to novel anduseful coated paper, methods of making this paper, and unique coatingcompositions employed therein. The coated paper of this inventionthrough the unique properties of its coating composition not onlypermits the application of any conventional method of printing used onconventional clay-coated papers; but in addition, it permits the uniquefeature of bonding these printed sheets together by the combinedapplication of heat and pressure to form a superiorly bound coated paperproduct such as a book, magazine, brochure, pamphlet, annual report,pad, envelope or similar product.

2. Description of the Prior Art Books and pamphlets are conventionallymade by fastening paper together by sewing, stapling or adhesivebinding. Each of these methods suffer from one or more of the followingshortcomings: low binding strength, poor permanence, failure to lie flatwhen opened, and high labor and cost of manufacture. The limitations ofthese methods are largely due to the characteristics of conventionalcoated printing papers, methods of quality printing such as letterpressand lithographic, and methods of reducing large printed sheets to booksize.

There are a number of materials that can be fastened together by bondingwith heat and pressure, such as certain plastic films and plasticfilm-paper laminations, and used in certain packaging applications; butall these, in general, suffer from the same problem of not being able tobe used for the high quality printing application that is common ofcoated printing papers. These materials are printed in less demandingapplications by the use of special pretreatment, special inks and withspecialized printing processes such as flexographic printing with rubberplates. These materials are not suitable for the production of highquality books and the like because of the above-mentioned printingquality shortcomings and the high cost of production.

This invention makes possible new methods of fastening quality printedpaper which overcome all the previously mentioned objectionssimultaneously, by basically altering the heat and pressure responsecharacteristics of conventional coated paper while still maintaining thedesirable qualities of conventional coated paper.

It has been known to produce thermal or heat-sensitive copy paper bycoating paper with a composition containing a resinous binder and opaquethermoplastic particles having a fusion or coalescing point above thedrying temperature used when applying the coating to paper. US. Pat.Nos. 3,228,785 and 3,306,763 disclosed such coated papers. Coated copypapers of this type rely on the transparentization of the opaquethermoplastic particles by application of heat at selected areassufficient to fuse or coalesce the thermoplastic particles. The additionof pigment particles which are infusible at the temperatures to whichthe paper is subjected defeats the purpose of the heat-sensitive coatingand such pigment particles are specifically excluded.

SUMMARY OF THE INVENTION The coated paper of this invention through thenature of its unique coating composition produces a bound printedproduct which has a superior, more durable bond than can exist by usingthe binding processes such as stapling, sewing, adhesive binding andmechanical binding now used with conventional clay-coated printingpapers since the bond formed with the novel coated paper extends overthe entire area pressurized, for example, which could run the fulllength of the bound edge. At the same time, the bound printed productmade from the coated paper in this invention produces a superior printedproduct at a lower cost than conventional heat sealing materials such asplastic films.

The coated paper of this invention obtains its unique printing andself-bonding properties through its unique combination of coatingcomposition components. In this coating composition, the presence of 20to 65 percent of discrete thermoplastic resin particles which remain asdiscrete particles through the drying operation when the coating isapplied to the paper substrate, but which will coalesce under thecombined application of sufficient heat and pressure to form a bond toitself or another similar sheet, gives this coated printing paper uniqueheat sealing properties not found in other coated printing papers. Thesediscrete thermoplastic resin particles in combination in this coatingcomposition with 15-75 percent of inorganic pigment(s) and 5-20 percentof resinous binder give this coated heat sealing paper printingproperties not found in any other heat sealing materials. Thiscombination of printing and heat scaling properties produces a coatedpaper which can be printed and formed into uniquely bound book andbook-like products.

BRIEF DESCRIPTION OF THE DRAWING The drawings presented which form apart of our specification, are rendered self-descriptive by the suitablelegends accompanying the drawings, wherein:

FIG. 1 is an enlarged diagrammatic cross-sectional view of two sheets ofone-side coated paper of this invention showing the random distributionof discrete thermoplastic particles and inorganic pigment particles heldtogether on the surface of a paper substrate by the resinous binderbefore the combined application of heat and pressure by a pressure andheat source also shown.

FIG. 2 is similar to FIG. 1 except after sufficient heat and pressurehave been applied to one area of the sheets to seal them together. FIG.2 shows that in the pressurized area, after the pressure has beenremoved and the sheet cooled below the coalescing temperature of thethermoplastic, there no longer exists discrete thermoplastic particlesbut coalesced thermoplastic masses common to both sheets of paper thusproviding a bonded area between the two sheets.

DESCRIPTION OF PREFERRED EMBODIMENTS The coated paper of this inventionobtains its unique heat and pressure-sensitive properties primarilythrough the incorporation in the coating composition of 20 to 65percent, preferably about 30 to about 45 percent, discrete thermoplasticresin particles, such as poly(vinyl chloride) or polystyrene which havecoalescing temperatures of at least about F. Because these thermoplasticresin particles do not coalesce at the temperatures used in drying thecoating composition on the paper substrate, the thermoplastic acts aspigment"-like particles and assists in imparting microporosity to thecoated sheet which is necessary for proper printing ink receptivity, inksetting, and ink drying characteristics, provided the resinous binder oradhesive portion of the coating composition is maintained atsufficiently low levels to avoid complete filling of the voids or porousnature of the coating.

The discrete thermoplastic particles used in this invention are notfilm-forming below their coalescing temperatures and, as particles, havelittle or no binding or adhesive power at room temperature as do manysomewhat similar materials used in conventional clay coated printingpapers for pigment binders, such as low fusing styrene-butadienecopolymers (60 percent styrene 40 percent butadiene). The discretethermoplastic particles have a coalescing temperature of at least bout140 F., preferably in the range of about 140 F. to about 400 F. Thispennits the coating to be dried during production of the coated paperwhile retaining the particulate nature of the thermoplastic. Only whenthe coated paper of this invention is subjected to the necessarycombination of heat and pressure during the bonding operation, whichbrings the sheets of paper into intimate contact, do these discretethermoplastic particles soften and coalesce with other suchthermoplastic particles in an adjacent coated sheet to form a strong,durable bond between the sheets upon cooling of the thermoplastic belowits coalescing temperature. Conventional clay-coated printing paperswill not form a sufficient bond under the application of heat andpressure because the level of thermoplastic binder is necessarily toolow. However, if the amount of room temperature film-formingthermoplastic resins used as pigment binders were increased to thenecessary level in conventional clay-coated printing paper to allowformation of an adequate bond under the application of heat andpressure, the printing properties would then be lost because themicroporosity of the sheet necessary for printing would have beenreduced too much or destroyed. Also, by the use of thermoplasticparticles that are non-film forming at temperatures below about 140 F.,the coated paper of this invention avoids premature or undesiredbonding, sticking, blocking, or marking tendencies at temperatures andpressures under which the coated paper is manufactured, handled and/orused.

The thermoplastic particles of this invention remain as discreteparticles during the drying of the applied coating, so long as the sheettemperature is not raised above the coalescing temperature of theparticles. The average particle size preferably ranges from about 0.2 toabout 5.0 microns. Because of these factors and the inherent lightreflectance and refractive properties of the thermoplastic particles,they contribute significantly to the opacity and brightness of theresulting coating. Particles of thermoplastic smaller than about 0.2micron were found to contribute very small opacity and brightnessbenefits to the coating while particles larger than five microns mightcontribute to print quality degradation.

Inasmuch as the thermoplastic resins suitable for use as thethermoplastic particles of the present invention comprise a broad groupthat does not readily lend itself to narrow and accepted chemicalclassification and have physical and chemical properties that are notcommon to every member of the group, the following method is provided toenable the easy determination of suitability and selection ofthermoplastic resins for use in this invention. One method which wasused to determine the coalescing temperature of thermoplastics was asfollows: Aqueous dispersions of the thermoplastic, for example, in thegeneral form supplied by the manufacturers at about 50 i 6 percentsolids, were drawn-down on 16-inchthick black glass plates using anapplicator bar which applied a 3 mil thickness wet coating. Thesecoatings were dried in an oven at various air temperatures from about 75F. through about 400 F. for 10 minutes and then observed to determine atwhat temperatures the coatings remained white and opaque, effectivelyhiding the black glass plate from view, and at what temperatures thecoatings lost their opacity and turned translucent or transparent,allowing the black plate to show through the resulting film. Thosethermoplastic coatings which remain opaque and do not form a transparentor translucent film at or below about 140 F. are considered to haveremained particulate in form and are acceptable from this standpoint foruse in the coating formulation.

Any thermoplastic particles can be utilized in the novel coatingcompositions so long as they remain as discrete particles and do not actas film-forming binder materials below about 140 F. but coalesce attemperatures above about 140 F., preferably in the range of about 140 F.to about 400 F. Included are those grades of polyvinyl chloride,polystyrene, styrene butadiene (80-99 percent styrene to l-20 percentbutadiene), vinyl chloride-vinylidene chloride copolymer,vinylchloride-vinylacetate copolymer, terpolymer of styrene, butadieneand acrylonitrile, gum rosin, polymerized rosin, polymerized rosinglycerol ester, partially dimerized rosin, acrylic polymers and powderedpolyethylene, having these characteristics.

In order to give the coated paper of this invention the desiredproperties of proper ink receptivity, ink holdout, ink drying andsetting characteristics, permanent opacity (especially at those areaswhich are heated and pressurized to form the bond), and favorableeconomics, the novel coating composition contains about to about 75percent, preferably about 40 to about 60 percent, of one or moreinorganic or organic pigments. The average particle size of the pigmentcan range from about 0.2 micron to about 5.0 microns. For example,inorganic pigments, such as, coating grade clay, calcium carbonate andTiO having average particle sizes of 1.0, 0.20 and 0.25 microns,respectively, have been used as components in the novel compositions.When a combination of inorganic pigments are used, maximum desiredproperties can be obtained, although the pigments can be effectivelyused individually. The type of inorganic pigment or combination in thenovel coating compositions has little influence on the bonds formedbetween the sheets when heat and pressure were applied. However, thehigher the pigment level in the coating, (requiring a consequentlowering of the thermoplastic resin particle level), the more the coatedsheets tend to become difficult to bond to each other, all otherconditions being equal. Non-thermoplastic pigments or pigments which donot coalesce below 400 F. are employed.

If colored sheets are desired, colored pigments or dyes can be used topartially replace the white pigments mentioned above, the degree ofreplacement depending on the desired hue.

The thermoplastic resin particles do not have sufficient binding oradhesive power (before activation by pressure and heat) to be utilizedwithout the addition of an additional binding or adhesive material tosecure the resin and pigment together in the coating layer and to thepaper substrate. To bind the inorganic pigment and the discretethermoplastic resin particles together in the coating layer and to bindthe coating layer to the paper substrate in order to produce a coatedpaper which has the necessary degree of surface strength to allow thepaper to be printed, particularly by the more demanding lithographicprinting process and which has the necessary flexibility to allow thepaper to be folded without cracking or weakening at the fold duringfolding and binding operations, about 5 to about 20 percent, preferablyabout 10 to about 15 percent organic resinous binder is used in thecoating composition. The microporosity needed in the coating of a coatedpaper to permit proper printing ink receptivity, holdout and dryingcharacteristics is not only dependent upon the particulate thermoplasticportion and the particulate pigment portion of the coating composition,but is also dependent on the amount of film-forming resinous binder usedin the coating. The binder must be used at sufficiently low levels toprevent complete filling of the voids or spaces in the coating.Thermoplastic resinous binders which are film-forming at or about roomtemperature, such as poly(vinyl alcohol) or styrene-butadiene copolymer(60 percent styrene-40 per cent butadiene), were found to enhance theease of bonding together of the coated sheets when subjected to heat andpres sure and in fact permit the reduction of the amount of discretethermoplastic resin needed in the coating composition. However, theorganic resinous binder need not be thermoplastic in order to practicethis invention. Any of the binders commonly used in the paper coatingarts can be employed.

The following is a non-limiting list of resinous binders which have beenutilized either singly or in combination with one another: poly(vinylalcohol), styrene-butadiene copolymer (60 percent styrene40 percentbutadiene), soya protein, and hydroxyethylated starch. Several otherswhich can be utilized include poly(vinyl acetate), acrylic polymers,casein and various starch binders.

Inasmuch as the content of the pigment particles and the thermoplasticresin particles affects the microporosity of the resulting coated paper,the total content of these particles should be in the range of about toabout 95 percent, preferably about to about percent, of the coating onthe dry weight basis.

The aqueous coating composition described in this invention can beapplied to both sides of a white opaque paper substrate, basis weightrange between 32 and lb. (25X38-500 by any conventional coating method,such as blade coating at coat weight levels from about 3 to about 15 lb.per side per ream and subsequently dried at a temperature below thecoalescing temperature of the thermoplastic particles by means of hotair or steam heated dryer cans or any other means which removes thewater or other inert vehicle from the coating so that the final coatedsheet has been 2 and 7 percent final moisture based on the dry weight ofpaper. The resulting coated paper product has a basis weight range from40 to 120 lb. (25X38-500) and has all the appearances and printingproperties of conventional clay-coated printing papers. In addition, theresulting coated paper permits a strong durable bond to be fonnedbetween sheets thereof brought into intimate contact under theapplication of heat and pressure and consequently permits books,pamphlets, brochures, and similar miltiple paper forms to be readilyproduced. A unique feature of this coated paper is its ability to bebound to similar sheets or to compatible plastic films, brought intointimate contact, under the application of suffcient heat and pressureto soften the discrete thermoplastic particles therein causing thesematerials to flow together under pressure to form a strong durable bondin the pressurized zone after cooling the sheets below the coalescingtemperature of the thermoplastic.

An important feature of the coated paper of this invention is that it isnon-heat and pressure sensitive within the temperature ranges ofpractical use and handling and that is non-heat and pressure sensitivebelow the fusion or coalescing temperatures of the thermoplastic resinparticles used in the coating composition. Also, this coated paper willnot form a bond to other similar paper by the application of pressurealone in the absence of sufficient heat to raise the temperature of thethermoplastic resin above its coalescing temperature or by theapplication of heat alone in the absence of sufficient pressure to putsuch sheets into intimate contact whereby the thermoplastic resin canflow and form binding points between the adjacent sheets.

Various chemical additives, which are commonly used in coatingformulations to produce specific coating or coated paper properties, canalso be used in the coating composition of this invention at normal uselevels without interfering with the desired printing and heat scalingproperties. Such materials include defoamers, antifoamers, flowmodifiers, lubricants, thickeners and insolubilizers. The solids contentof the novel composition can be varied in the range of about 20 to about60 percent, depending on the method of application. For blade coating arange of about 50 to about 60 percent solids is preferred, and for sizepress coatings about 20 to about 40 percent solids is preferred.

In preparing the coating compositions, two basic procedures can befollowed. With natural resinous binders and some synthetic adhesives, itis necessary to solubilize the material in the well known manner througha heat or chemical treatment or a combination of both in order to obtainthe binding properties of the material upon drying of the coating. Withthe first procedure, if a resinous binder of this nature is to be used,the material in the dry powder form is blended into an aqueousdispersion of a certain solids content of the pigment particles. Themixture of pigment particles, unsolubilized resinous binder, and wateris then subjected to the necessary heat and/or chemical treatment,following procedures outlined by the manufacturer of the resinousbinder, to achieve solubilization. After cooling the mixture to atemperature below the coalescing temperature of the thermoplastic resin,the thermoplastic resin particles, in aqueous dispersion form asreceived from the manufacturer, are blended into the above describedmixture. If an additional resinous binder of the type that requires nosolubilization to achieve binding properties is to be used, it isblended into the coating composition next. When additives to improve thecharacteristics of the coating composition are used, they are blendedinto the mixture last, usually in the sequence of flow modifiers firstand insolubilizers last.

With the second basic procedure for preparing coating compositions, if anatural or synthetic resinous binder requiring solubilization is used,it is prepared by itself, independent of the pigment dispersion, bydispersing the binder in the dry powder form in a certain specifiedquantity of water and then subjecting the blend to the necessary heatand/or-chemical treatment to achieve solubilization. The aqueous,solubilized form of the resinous binder is then added to an appropriateamount of inorganic pigment dispersion and the additional components ofthe coating composition are then added in the sequence described abovefor the first basic procedure for coating make-up. If desired, otherinert vehicles may be used in place of water, although water is by farpreferred because of economy, ease of handling and availability.

While paper is the preferred substrate other substrates to which theselected resinous binder will adhere can be used. For example,paperboard, cardboard, plastic films, and the like can be employed. Thethickness of the substrate also is not narrowly critical and can fall inthe range of about 2.5 mil to about 8.0 mils thickness.

There are many acceptable methods of heat sealing which can be used withthe coated paper of this invention. The four major factors whichprimarily influence the strength of the bonded area are: (l) the powerinput which is responsible for heating the coating to the coalescingtemperatures of the thermoplastic resin particles which varies for thedifferent chemical types of thermoplastic resin used in this inventionfrom about 140 F. to about 400 F., for example, (2) the pressure appliedduring heating which varies with thermoplastic resin type and amount ofthermoplastic resin in the coating used in this invention from about 30psi. to about 2,500 p.s.i. (3) the unit of time over which the heat andpressure were applied which varies with type of thermoplastic resin andthe amount of thermoplastic resin as well as the heat input and pressureapplied from as little as about 0.25 second to several seconds, e.g., 60seconds, and (4) the width of the bonded area formed which can be variedfrom about one-sixteenth inch or less to about 1/4 inch or more.Excellent seals have been made with the coated paper of this inventiondepending on the combination of the above mentioned variables usingeither impulse type heating or radio frequency (RF) type heatingdevices. Other methods of heat sealing can be used and the invention isnot limited to these two heat sealing devices. In general, the sealstrengths have been judged adequate when, upon stressing, bond failureoccurred in the paper substrate and not in the bond or at the interfacebetween bonded sheets along the entire area of the seal.

Several examples of coating compositions which were found to produce thedesired printing and heat sealing properties, in which, unless otherwisedesignated, all temperatures are in F., all parts and percentages are byweight and all the percentages listed for coating components are basedon dry weight percentages of the total dry solids content of the coatingcompositions, are presented.

EXAMPLE 1 A coating composition comprising:

Thermoplastic ResinPoly(vinyl chloride) as an aqueous latex,manufactured and sold as Geon 151 by the B. F. Goodrich ChemicalCompany, containing about 56% solids poly( vinyl chloride), having acoalescing temperature above 250 F. and an average particle size ofabout 0.2 microns Inorganic Pigments( 1) Clay Pigment (manufactured byEnglehard Minerals and Chemicals Corp. and available as Ultra Whitehaving 92-94% of particles less than 2.0 microns (2) Calcium CarbonatePigment (manufactured by Wyandotte Chemical and available as Purecal-O)having a particle size of 0. l0-O.35 microns Resinous BinderPoly( vinylalcohol),

manufactured by E. l. DuPont and available as Elvanol 7l-30), having amolecular weight of 50% calcium stearate l.0 Binderlnsolubilizer-Glyoxal as an aqueous solution containing 40% glyoxal 0.25Total: 100.05

was prepared by the previously described first basic procedure where theresinous binder is cooked in the presence of pigment and watersufficient to adjust the solids content to 50.6 percent solids. Thecomposition was applied to both sides of 3.0 mil thick white base paperat 10 to 13 lbs. per ream (total of both sides) using a trailing bladecoater and the coated paper was dried with forced hot air at 220 F. forseconds per side. The coated paper was rewound and sheeted. Some of thepaper was supercalendared to enhance its gloss to a value comparable toother commercial glossy coated printing papers.

EXAMPLE 2 A coating composition comprising:

was prepared to 46 percent solids as described in Example 1. Thecomposition was applied to both sides of 3.0 mil thick white base paperat a total of 8 to lbs. per ream (total of both sides) using a trailingblade coater. The coated paper was dried with forced hot air at 220 F.for 5 seconds per side.

Table l represents a comparison of the papers of this invention withconventional coated printing papers and with a selected plastic "paper",and a plastic-coated paper. Coated papers of the invention were thosemade in Examples 1 (unsupercalendared paper), and 2. Papers A through Drepresent typical commercial coated printing papers. Paper A1 is a sheetof typical paper that has bound on it a layer of extruded polyethylene.Paper B1 is an imitation paper, made entirely from a plastic materialand is known as Ucar, manufactured by Union Carbide.

T-480 respectively. The K & N Receptivity Test was performed similar toTAPPI Routine Control Method RC-l9, except that the dyed test ink wasleft on the paper being tested ,for only one minute instead of theprescribed two minutes.

After the test was completed, a G. E. Brightness value was obtained onthe tested area of the paper and this value was divided by the originalbrightness of the paper and multiplied by 100, yielding a value known asthe percent brightness retained by the test area. The lower this value,the more receptive the paper is to the ink.

Coated printing papers must achieve a balance between ink receptive andink holdout properties. Too much ink holdout could result in ink dryingproblems that might cause set-off of ink to sheets placed on top of theprinted sheet, or even more serious, the sheet may not even accept anormal printing ink. 0n the other hand, coated printing papers mustexhibit a certain amount of ink holdout for glossy prints and gooddefinition.

To further compare these papers for ink receptivity and ink set-offcharacteristics, an ink-set off test was performed using the lGTPrintability Test in conjunction with the Westvaco mm. Printing Disc.The ink used was lPl Speed King Process Blue Litho Ink. Generally, thisprocedure consists of metering ink onto the Westvaco Disc, transferringthis ink at 50 kg pressure and M speed setting using the IGTPrintability Tester to the sample being tested, and then after aspecified time (the samples in Table I were tested after min.), placinga sheet of the same paper on top of the printed paper, clamping bothsamples in the tester, and putting an impression on both samples usingthe IGT 20 mm Printing Disc at a pressure of kg. This impressionpressure causes undried ink on the original printed sample to set-off tothe superimposed sample. The degree of ink set-off was measured by usinga Densichron, manufactured by W. M. Welch Scientific Company, Chicago,111., with the red filter and obtaining a percent transmission readingon the set-off area first by setting the instrument to read 100 percenttransmission on the unprinted paper and then obtaining the reading ofthe ink set-off area. Therefore, the higher this value, the more lightis reflected from the paper surface and the less set-off of ink hasoccurred.

Heat seals were made with both a Radio Frequency (RF) and impulse heatsealer. With the Radio Frequency Sealer pressure of 2,300 p.s.i. andheat at a temperature range of 300-350 F. were applied over an area 4in. X l/ 16 in. for 0.25 sec. With the impulse sealer, pressure of 233p.s.i. and heat at a temperature of 300350 F. were applied over an area1 in. X H2 in. for4sec.

Heat seal strength was measured by employing a peel-type tensile test onthe sealed sheets. For sheets sealed by RF, a 3- inch width seal wasmeasured; for sheets sealed with the impulse sealer, a l-inch width sealwas tested. The test was conducted by clamping the ends furthest fromthe seal of the respective bonded sheets in special jaws of an InstronTensile Tester and the force required to peel the sheets apart wasmeasured in lbs. per inch.

TABLE I Papers of invention Conventional coated Plastic coated orprinting papers plastic paper Example Example Tests 1 2 A B C D A1 B1 G.E. brightness 83. 7 76. 9 77. 8 82. 3 81. l 80. 5 74. 6 86 8 Opaci y 93.0 88. 0 92. 1 93. 6 93. 5 95.0 91. 5 88 2 G 055 s. 18. 5 12.0 13. 0 8. 016. 0 68. 0 55. 0 35- 0 K and N ink receptivity (percent brightnessretained) 67. 3 75. 8 68. 0 57. 0 61. 8 76. 3 98. 2 91. 7 Ink set-ofi(percent transmission) 97. 7 71. 5 89. 5 80.1 92.9 80. O 24. 8 41. 2Heat seal strength RF sealinglbs./in 0. 46 0.62 None None None None 0 82None Heat seal strength impulse sealing-lbs./in 0. 68 0.58 None NoneNone None 1 34 1. 64

The G. E. Brightness, Opacity, and Gloss tests were run according toTAPPI Standard Test Methods T-452, T-425, and

From the results of Table I, it is apparent that the papers of theinvention are comparable to the conventional coated printing papers inoptical and ink receptive properties. The plastic coated and plasticpaper vary in optical properties but could compare to conventionalcoated papers. However, the ink receptive and set-off characteristics ofthese papers is so poor that normal printing inks could not be used toprint them conventionally.

The seal strengths of the papers of this invention are not as great asthe plastic or plastic-coated papers. However, the seals of the papersof the invention are adequate for binding by nature of the seals fiberpulling ability when peeled apart.

was prepared by the previously described second basic procedure wherethe resinous binder is cooked in the presence of water only and then theingredients blended together, and water was added to adjust the solidscontent to 42 percent solids. The composition was applied to both sidesof 3.0 mil thick white base paper at 12 lbs/ream (total of both sides)using a Mayer Rod. The coated paper was dried with forced hot air at220' F. for seconds per side.

was prepared to 42 percent solids in the manner described in 5' Example3 and was applied to both sides of 3.0 mil thick white base paper at 12lbs/ream (total of both sides) using a Mayer Rod. The coated paper wasdried with forced hot air at 220 F for 5 seconds per side.

EXAMPLE 5 A coating composition comprising:

Thermoplastic Resin-Poly(vinyl chloride) as described in Example 1 20.0Inorganic Pigment-Clay pigment as described in Example 1 60.0 ResinousBinder-Hydroxyethyl ether substituted starch as described in Example 320.0 Total: 100.0

was prepared to 45 percent solids in the manner described in Example 3and was applied to both sides of 3.0 mil thick white base paper at 12lbs/ream (total of both sides) using a Mayer Rod. The coated paper wasdried with forced hot air at 220 F. for 5 seconds per side.

EXAMPLE 6 A coating composition comprising:

Thermoplastic Resin-Poly( vinyl chloride) as described in Example 1.20.0 Inorganic Pigment-Clay pigment as described in Example I. 75.0Resinous Binder-Poly(vinyl alcohol) as described in Example 3 5.0 Total:100.0

was prepared to 52 percent solids in the manner described in Example 3and applied to both sides of 3.0 mil thick white base paper at 13lbs/ream (total of both sides) using a Mayer Rod. The coated paper wasdried with forced hot air at 220 F. for 5 seconds per side.

TABLE II Test results of Examples H K and N ink receptivity, G. Epercent Heat seal Opacbn'ghtbrightness strength, Example ity ness Glossretained lbs/in.

Table II lists the test results of Examples 3-6. These Examples utilizedthe approximate limits set forth for the compositions of this invention.From the results given, it is evident that the coated papers of theseExamples were very close in optical and ink receptive properties to thetypical commercial coated printing papers listed in Table l.

Table II also illustrates that the coated papers of these Examples wereheat sealable, using conditions of RF heat sealing described in respectto Table I. All seals resulted in fiber rupturing bonds and were fullyadequate for binding purposes.

EXAMPLE 7 The same composition as in Example 2 was prepared except thatit was prepared to 28 percent solids and applied at 8 to 9 lbs. per reamusing a size press.

EXAMPLE 8 A coating composition comprising:

Thermoplastic Resin-Styrene-butadiene copolymer as described in Example2 20.0 Inorganic Pigment-Calcium carbonate as described in Example 175.0 Resinous BinderPoly( vinyl alcohol) as described in Example 1 5.0

Total: 100.0

was prepared to 48.6 percent solids in the manner as described inExample 2 was applied to 12 lbs. per ream (total of both sides) to 3.0mil thick white base paper using a Mayer Rod. The coated paper was driedwith forced hot air at 220 F. for 5 seconds per side.

. 1. EXAMPLE 9 A coating composition comprising:

EXAMELE 12 Wt. Wt.

Thermoplastic Resin Swrenebutadiene. Thermoplastic Resin-Polystyrene asdescribed in acrylonitrile terpolymer (manufactured by ExamPle 1 MarbonChemical Co., and available as Marmix n? T I) f i fif d 16123) as a 52%solids aqueous dispersion of the ggg zg s gg f 't' z grade terpolymercomammg. 80-85% Polymcnzed coating clay, HT Predispersed slurry, havingan Styrene and less, average particle size of 0.8 microns 57.0 than 5%acrylonitrile, having an average particle (2) calcium carbonate Pigmentas described size of 0.1 microns and coalescing temperature of inExample 1 60 about Resinous Binder-Poly( vinyl alcohol) as describedInorganic Pigmem-Calcium carbonate pigment as 1 5 in Example 1 70described in Example 1 50.0 Total: 1000 Resinous Binder-Poly( vinylalcohol) as described in Example 3 7.5 Total: 100.0

was prepared to 45.6 percent solids in the manner described in Example Iand applied to both sides of 3.0 mil thick white was prepared to 37percent solids in the manner as described paper at 8 to 10 per ream(total of sldejs) 3 trailing blade coater. The coated paper was driedwith forced in Example 3 and applied to both sides of white base paperat hot air at 220 F for 5 Seconds p Side 6 to 10 lbs. per ream (total ofboth sides) using a Time-Life Bench Coater. The coated paper was driedwith forced hot air A P 13 at 220 F. for 5 seconds per side.

A coating composition comprising: EXAMPLE 10 Wt. A coating compositioncomprising:

wt Thermoplastic Resin-Polystyrene as described in Example 11 30.0

Inorganic Pigments( l Clay pigment as described in Exam le 1 49.5Thennoplastic Res1n-Vinyl chloride copolymer as galcium carbonate p g asdescribed a 56% solids aqueous dispersion having an in Example 1 5'5pamcle Slze of mlcmns a Resinous Binder-Styrene-butadiene copolymer ascoalescmg temperamre of aboYc 250 a 50% solid aqueous dispersion ofcopolymer (manufactured by B. F. Goodrich Chemical Co. consisting f 60Paris polymerized styrene, 40 and avallfiblc as Gcon 1) 620 partspolymerized butadiene, and manufactured inorganic Pigment-Calciumcarbonate pigment as by Dow Chemical Co and available as Dow describedin Example 1 40 Latex 620 15.0 Resinous BinderPoly(viny1 alcohol) asdescribed Total. 1000 in Example 3 5.0 Total: 100.0

was prepared to 60 percent solids in the manner described in g Example 3and applied to both sides of 3.0 mil thick white was prepared to 46percent solids in the manner described in base paper at 95 to 12 perream (total of both Sides) using Examplc 3 and PP to both of thick f aMayer Rod. The coated paper was dried with forced hot air base paper atl l-l 2 lbs. per ream (total of both sides) using a at 220 fo 5 Secondsper Side. Mayer Rod. The coated paper was dried with forced hot air at 5seconds per side. 50 EXAMPLE [4 EXAMPLE H A coating compositioncomprising: A Coatmg composmon compnsmg:

Wt. Wt. '77

Thermoplastic ResinPoly( vinyl chloride as ThermoplasticResin-Polystyrene as a 50% sol ds described in Example 1 29 aqueousdispersion and havng an Inorganic Pigments( l Clay pigment as describedparticle size of 0.2 microns and a coalescing in Example I 51.50temperature of about 300 F. (manufactured by (2) C l i carbonatc pigmentas d ib d Dow Chemical Co., and available as Dow Latex in Example I 8.50586) Resinous Binders( l) Poly(vinyl alcohol) as Inorganic Pigments( 1)Calcium carbonate described in Example 1 4.45

pigment as described in Example I 25.0 (2) Styrene-butadiene as a 50%solids (2) Clay pigment as described in Example 1 25.0 dispersion ofcopolymer consisting of 60 Resinous Binder-Poly(vinyl alcohol) asdescribed parts polymerized styrene and 40 parts in Example 1 5.0polymerized butadiene, and manufactured Total; [000 by theSinclair-Koppers Co., and available as SinclaiFKoppers Latex K-55 E 4.45Flow Modifiers( l) Carboxymethyl cellulose, manufactured by Hercules,Inc., and available as Cellulose Gui-n, grade 7 m, and having 0.65 towas prepared to 46 percent solids in the manner described in 0.85carboxymethyl groups per Gum Example 1 and applied to both sides of 3.0mil thick white anhydroglucose unit, molecular weight 10,000, base paperat 8-10 lbs. per ream (total of both sides) using a fg gfliz gzgiggcfiggersion as described 0.25 Time-Life Bench Coater. The coated paperwas dried with in Example 1 L00 forced hot air at 220 F. for 5 secondsper side. 7 Insolubilizer-Glyoxal as described in Example 1 0.25

Total: 100.00

was prepared to 53 percent solids in the manner described in Example 1and was applied to both sides of 3.0 mil thick white base paper at l lto 12 lbs. per ream (total of both sides) using a Mayer Rod. The coatedpaper was dried with forced hot air at 220 F. for seconds per side.

EXAMPLE 15 A coating composition comprising:

was prepared to 56 percent solids in the manner described in Example 1and was applied to both sides of 3.0 mil thick white base paper at 12-13lbs. per ream (total of both sides) using a Time-Life Bench Coater. Thecoated paper was dried with forced hot air at 220 F. for 5 seconds perside.

EXAMPLE 16 The same procedure as described in Example 15 was carried outexcept the 4.6 percent soybean protein was replaced with 4.6 percenthydroxyethyl ether substituted starch, as described in Example 3.

EXAMPLE 17 A coating composition comprising:

Thermoplastic Resin-Glycerol ester of polymerized rosin, as a 40%aqueous dispersion of said polymer which has a molecular weight of l100, with 90% of particles having a particle size of 1 micron and amaximum particle size of 3 microns and a coalescing temperature of about250 F manufactured by Hercules, lnc., and available as Dresinol 155Inorganic PigmentClay pigment as described in Example 1 ResinousBinder-Poly( vinyl alcohol) as described in Example 3 7.0 Total: 100.0

was prepared to 42.5 percent solids in the manner described in Example 3and applied to both sides of 3.0 mil thick white base paper at 13 lbs.per ream (total of both sides) using a Mayer Rod. The coated paper wasdried with forced hot air at 220 F. for 5 seconds per side.

EXAMPLE 18 A coating composition comprising:

Thermoplastic Resin-Powdered polyethylene,

average particle size 30 micron, melt index 5,

having a coalescing temperature of 300 F manufactured by U. S. 1.Chemicals, and available as Microthene FN 510 Microfine PolyethylenePowder 30.0 Inorganic Pigment-Clay pigment as described in Example 163.0 Resinous Binder-Poly( vinyl alcohol) as describe in Example 1 7.0Total: 100.0

was prepared to 42-43 percent solids in the manner described in Example1 and applied to both sides of 3.0 mil thick white base paper at 13 lbs.per ream (total of both sides) using a Mayer Rod. The coated paper wasdried with forced hot air at 220 F. for 5 seconds per side.

The coated papers produced in Examples 7 through 18 were each very closein optical and ink receptive properties of typical conventional coatedprinting papers such as those listed in Table l. The coated papers ofExamples 7 through 18 were each heat scalable, using conditions of RFheat sealing described in respect to Table l and the seals formed wereall fully adequate for binding purposes.

What is claimed is:

1. Coated printing paper characterized by printing properties which arecharacteristic of clay-coated printing papers and in being bondable toitself by application of heat and pressure in selected areas to form abound coated paper product such as a book, magazine, brochure, pamphlet,annual report, pad, envelope, or other printed paper products havingbonded on at least one of its surfaces a coating comprising,

A. about 20 to about 65 percent discrete thermoplastic particles whichare capable of forming an opaque coating from a dispersion thereof andremain discrete when dried at temperatures below about F. and whichcoalesce at temperatures of not less than about 140 F., the

average particle size of said discrete thermoplastic particles beingless than about thirty microns,

B. about 75 to about 15 percent opaque pigment particles of an averageparticle size in the range from about 0.2 to about 5 microns, and

C. about 5 to about 20 percent binder which is film-forming betweenabout room temperature and a temperature below about 140 F. for bindingsaid thermoplastic particles and pigment particles together and to saidpaper,

said percentages being based on the total dry weight of said coating,the coat weight level of said coating being in the range from about 3 toabout 15 pounds per side per ream (25X38-), said coated paper beingbondable by pressure and heat sufficient to coalesce discretethermoplastic particles and at temperatures below the temperature atwhich the paper deteriorates.

2. Coated paper as claimed in claim 1 wherein said thermoplasticparticles coalesce at about 140 to about 400 F.

3. Coated paper as claimed in claim 1 wherein said pigment particles arecalcium carbonate particles.

4. Coated paper as claimed in claim 1 wherein said pigment particles aretitanium dioxide particles.

5. Coated paper as claimed in claim 1 wherein said pigment particles areclay particles.

6. Coated paper as claimed in claim 1 wherein said thermoplasticparticles are poly(vinyl chloride) particles.

7. Coated paper as claimed in claim 1 wherein said thermoplasticparticles are styrene-butadiene copolymer particles.

8. Coated paper as claimed in claim 1 wherein said discretethermoplastic particles are styrene-butadiene-acrylonitrile terpolyrnerparticles.

9. Coated paper as claimed in claim 1 wherein said discretethermoplastic particles are vinyl chloride-vinyl acetate copolymerparticles.

10. Coated aper as claimed in claim 1 wherein said discretethermoplastic particles are polystyrene particles.

11. Coated paper as claimed in claim 1 wherein said discretethermoplastic particles are polymerized rosin glycen'de particles.

12. Coated paper as claimed in claim 1 wherein said discretethermoplastic particles are polyethylene particles.

13. Coated paper as claimed in claim 1 wherein said binder is poly(vinylalcohol) which is film forming at a temperature below about 140 F.

14. Coated paper as claimed in claim 1 wherein said binder ishydroxyethyl ether substituted starch which is film forming at atemperature below about 140 F.

15. Coated paper as claimed in claim 1 wherein said binder isstyrene-butadiene copolymer which is film forming at a temperature belowabout 140 F.

16. Coated paper as claimed in claim 1 wherein said binder is proteinwhich is film forming at a temperature below about 140 F.

17. A paper article comprising a plurality of sheets of coated paper asclaimed in claim 1, the thermoplastic particles of the coating of one ofsaid sheets being coalesced with the thermoplastic particles of anotherof said sheets.

18. Method of manufacturing coated paper which is printable and bondableby heat and pressure comprising the steps of applying to paper acomposition comprising in an inert vehicle a mixture containing A. aboutto about 65 percent discrete thermoplastic particles which are capableof forming an opaque coating from a dispersion thereof and remaindiscrete when dried at temperatures below about 140 F. and whichcoalesce at temperatures of not less than about F., the average particlesize of said discrete thermoplastic particles being less than about 30microns,

B. about 75 to about 15 percent opaque pigment particles of an averageparticle size in the range from about 0.2 to about 5 microns, and

C. about 5 to about 20 binder which is film-forming between about roomtemperature and a temperature below about 140 F. for binding saidthermoplastic particles and pigment particles together and to saidpaper,

said percentages being based on the total dry weight of the above listedcomponents A, B and C, and thereafter removing the inert vehicletherefrom.

19. Method of manufacturing a paper article as claimed in claim 17comprising contacting the coated surfaces of a plurality of sheets ofcoated paper as claimed in claim 1 with each other in the area desiredto be bonded and compressing said sheets together in said area at apressure of at least about 30 p.s.i. while heating the contacted coatedsurfaces in said area to a temperature sufficient under the appliedpressure to cause the thermoplastic particles in the coating to coalesceand cooling to bond said sheets together.

20. Method as claimed in claim 19 wherein printing is applied to thecoated surface of said sheets.

2. Coated paper as claimed in claim 1 wherein said thermoplasticparticles coalesce at about 140* to about 400* F.
 3. Coated paper asclaimed in claim 1 wherein said pigment particles are calcium carbonateparticles.
 4. Coated paper as claimed in claim 1 wherein said pigmentparticles are titanium dioxide particles.
 5. Coated paper as claimed inclaim 1 wherein said pigment particles are clay particles.
 6. Coatedpaper as claimed in claim 1 wherein said thermoplastic particles arepoly(vinyl chloride) particles.
 7. Coated paper as claimed in claim 1wherein said thermoplastic particles are styrene-butadiene copolymerparticles.
 8. Coated paper as Claimed in claim 1 wherein said discretethermoplastic particles are styrene-butadiene-acrylonitrile terpolymerparticles.
 9. Coated paper as claimed in claim 1 wherein said discretethermoplastic particles are vinyl chloride-vinyl acetate copolymerparticles.
 10. Coated paper as claimed in claim 1 wherein said discretethermoplastic particles are polystyrene particles.
 11. Coated paper asclaimed in claim 1 wherein said discrete thermoplastic particles arepolymerized rosin glyceride particles.
 12. Coated paper as claimed inclaim 1 wherein said discrete thermoplastic particles are polyethyleneparticles.
 13. Coated paper as claimed in claim 1 wherein said binder ispoly(vinyl alcohol) which is film forming at a temperature below about140* F.
 14. Coated paper as claimed in claim 1 wherein said binder ishydroxyethyl ether substituted starch which is film forming at atemperature below about 140* F.
 15. Coated paper as claimed in claim 1wherein said binder is styrene-butadiene copolymer which is film formingat a temperature below about 140* F.
 16. Coated paper as claimed inclaim 1 wherein said binder is protein which is film forming at atemperature below about 140* F.
 17. A paper article comprising aplurality of sheets of coated paper as claimed in claim 1, thethermoplastic particles of the coating of one of said sheets beingcoalesced with the thermoplastic particles of another of said sheets.18. Method of manufacturing coated paper which is printable and bondableby heat and pressure comprising the steps of applying to paper acomposition comprising in an inert vehicle a mixture containing A. about20 to about 65 percent discrete thermoplastic particles which arecapable of forming an opaque coating from a dispersion thereof andremain discrete when dried at temperatures below about 140* F. and whichcoalesce at temperatures of not less than about 140* F., the averageparticle size of said discrete thermoplastic particles being less thanabout 30 microns, B. about 75 to about 15 percent opaque pigmentparticles of an average particle size in the range from about 0.2 toabout 5 microns, and C. about 5 to about 20 binder which is film-formingbetween about room temperature and a temperature below about 140* F. forbinding said thermoplastic particles and pigment particles together andto said paper, said percentages being based on the total dry weight ofthe above listed components A, B and C, and thereafter removing theinert vehicle therefrom.
 19. Method of manufacturing a paper article asclaimed in claim 17 comprising contacting the coated surfaces of aplurality of sheets of coated paper as claimed in claim 1 with eachother in the area desired to be bonded and compressing said sheetstogether in said area at a pressure of at least about 30 p.s.i. whileheating the contacted coated surfaces in said area to a temperaturesufficient under the applied pressure to cause the thermoplasticparticles in the coating to coalesce and cooling to bond said sheetstogether.
 20. Method as claimed in claim 19 wherein printing is appliedto the coated surface of said sheets.